Modular furnace and methods of repairing same

ABSTRACT

A refractory furnace (10) is constructed to facilitate repair of worn or damaged refractory portions while the furnace is maintained at near-operating temperature. A sidewall (40) of the refractory furnace is comprised of a plurality of modular sections (85) each of which includes a refractory lining (87). One or more modular sections may be selectively replaced when becoming worn or damaged. Replacement is accomplished by external access and removal of the worn or damaged modular sections.

TECHNICAL FIELD

This invention relates to a modular furnace and to methods of repairingsame. More particularly, it relates to a furnace which facilitatesremoval and replacement of damaged or worn modular refractory portionsthereof from the outside of the furnace.

BACKGROUND OF THE INVENTION

A refining furnace or oven structure is often constructed of refractorybricks lining the inside of a metal frame. The furnace structureincludes a bottom portion comprising refractory brick and otherrefractory lining materials so arranged as to form a leak-tightreservoir wherein a molten metal resides. The structure also includes aroof portion and a sidewall portion. The bottom, roof and sidewallportions form the receiving volume for a refinable metal charge andisolate and insulate an interior heat source. A typical heat source is anatural gas flame.

Refractory brick is composed of various refractory oxides includingmagnesium, chromium, aluminum and silicon oxides which are formed in theshape of rectangular parallelepipeds. Bricks are supported by variousmeans depending on the structure constructed. The bottom portion of thefurnace structure is comprised of bricks positioned with one end exposedto the furnace interior and the other end engaging and being supportedby the metal furnace frame. Bricks comprising the sidewall portion maybe supported by the metal furnace frame with sufficient layers of bricksstacked one upon another to provide a desired wall height.Alternatively, wall portions may be built up from bricks with integralmetal hangers attached to the metal frame over the entire height of thesidewall. Bricks comprising the roof portion may be supported with metalplates as is disclosed in U.S. Pat. No. 4,529,178, wherein, brickssupported by metal plates are hung from metal support members.

Portions of brick exposed to the heat source and molten metal aresubject to corrosion, wear and mechanical damage. Extreme temperatures,corrosive slag and chemically reactive atmospheres containing, forexample, sulphur, carbon monoxide and carbon dioxide and various acidfumes all act to burn away the brick material. Mechanical damagecompounds with thermochemical wear and results in portions of thefurnace wearing more quickly than other portions. For example, thesidewall portion of the furnace under the influence of high temperature,corrosive atmosphere and mechanical damage caused, for example, by theintroduction of a furnace charge, wears more quickly than the roofportion. Wear may proceed to a point wherein the worn portion mayrupture. When rupture occurs, flames originating from the interior heatsource may escape, or if the rupture is below the surface of the moltencharge, molten metal will leak from the furnace.

Prior art repair techniques include those where maintenance personnelenter the furnace and rebuild damaged or worn portions. Thedisadvantages of this method are that the entire furnace must be emptiedand cooled to permit safe entry by the maintenance personnel and thatthe time required for the repair is lengthy. Because of the furnace'slarge thermal mass and a typical operating temperature in excess of2000° F, the time required to cool the furnace can be in excess of twoweeks. Other methods allow direct access to the interior of the furnaceby personnel without a complete furnace cool-down. Such a method whichis disclosed in U.S. Pat. No. 4,452,749 necessitates the cooling of thefurnace or oven to a brick surface temperature of about 500° F.Maintenance personnel wearing protective clothing with integral coolingsystems enter the oven and repair portions of the furnace brickstructure. This method is potentially hazardous and requires substantialcooling and the subsequent reheating of the furnace.

Other methods of repair include those that do not require furnace entrydirectly by repair personnel. An external access method includes agunning technique wherein a refractory repair material is sprayed intothe damaged or worn region as disclosed in U.S. Pat. Nos. 4,779,798 and4,465,648. Although there appears to be no requirement of furnace cooldown to effect this method, use of the gunning technique results innon-uniformity of the repaired portions and shorter useful life than theoriginal refractory material.

Another external access method is disclosed in U.S. Pat. No. 4,017,960where a damaged portion is removed from the furnace by cutting through asteel support structure and through the damaged refractory portion. Thecut is made approximately around the perimeter of the damaged or wornportion. The damaged or worn portion described is removed and replacedby a section of similar refractory material which has been cut in ashape complementary to the shape of the opening remaining in the furnaceshell and refractory lining. This method disadvantageously requires acustom shaping of the section which is inserted into the opening of thefurnace sidewall.

What is needed and what does not appear to be provided in the prior artis a furnace which is constructed so as to facilitate repair. Generally,the sought-after furnace should be one for which repairs may be madefrom outside the furnace without the need to cool down completely thefurnace during such repair.

SUMMARY OF THE INVENTION

The just described problems of the prior art have been overcome with thefurnace and the methods of repairing same of this invention. A furnaceof this invention includes a furnace structural frame and an interiorrefractory lining supported by and in attachment to the furnacestructural frame. The refractory lining comprises a bottom portion whichforms a leakproof reservoir for containing molten material, a roofportion which is positioned above the bottom portion and a sidewallportion which is disposed between the bottom portion and the roofportion. The sidewall portion is comprised of a plurality of individualmodules and is designed so as to facilitate repair of the sidewallportion by allowing selective removal and replacement of the individualmodules as they become damaged or worn. The modules which may also bereferred to as modular sections may be constructed of a refractory brickmaterial attached to an external support structure. Alternatively, acast, monolithic refractory element may be used in place of therefractory brick material. A module is replaced when excessive damage orwear has been sustained by a section of the sidewall. Evidence of thiscondition may be flames exiting from the sidewall, visual evidence oflost refractory material, unusually high levels of refractory impuritiesin the furnace's slag run-off and loss of furnace efficiency.

To effect replacement of a sidewall modular section, the furnace heatsource is shut down or attenuated as required. An external liftmechanism is moved into position adjacent to the section that requiresremoval and is engaged therewith. A wedge shape key refractory blockdisposed between the modular section and the roof portion is removed byhand by a furnace rebuild technician. A mechanical securing means,located adjacent to the roof portion, which secures the sidewall modularsection external support structure to the furnace structural frame, isreleased. The external lift mechanism is moved away from the furnacestructure causing the modular section to be removed from the sidewallportion. A new or rebuilt modular section is mounted on the externallift mechanism and is repositioned in the sidewall void created by theprior modular section removal. This replacement procedure is applicableto the replacement of sidewall modular sections which utilize therefractory brick refractory elements or the cast, monolithic refractoryelement. Once the modular section is in place, the furnace heat sourcemay be re-ignited or turned up to resume normal operation.

Advantageously, the furnace of this invention does not have to be cooledsubstantially prior to repair of replacement of the modular sections.Repair is accessed from the outside of the furnace and is thereforeeasier and more convenient than some other furnace repair techniques.New wall sections of materials identical to refractory materials inshape and material used in other portions of the furnace may be used forthe repair instead of gunned refractory materials. This repair methodcan be repeated so that the entire useful lives of other portions of thefurnace are realized. Long cool-down and heat-up periods are avoidedalong with the costs normally associated therewith.

BRIEF DESCRIPTION OF THE DRAWING

Other features of the present invention will be more readily understoodfrom the following detailed description of specific embodiments thereofwhen read in conjunction with the accompanying drawings, in which:

FIG. 1 is a cross sectional view of a furnace of this invention;

FIG. 2 is a cross sectional view of a furnace of the prior art;

FIG. 3 is a front elevational view of a modular section comprised of aplurality of refractory brick;

FIG. 4 is a side elevational view of the modular section of FIG. 3;

FIG. 5 is a side elevational view of a modular section comprised of a 20cast, monolithic refractory element; and

FIG. 6 is a perspective view depicting a step in the replacement of amodular section.

DETAILED DESCRIPTION

Referring now to FIG. 1, there is shown a refractory furnace which isdesignated generally by the numeral 10. As can be seen in the drawing,the furnace 10 includes a tilt follower beam 12 supported by a pluralityof rollers 14-14. A hydraulic cylinder 16 actuates a tilting motion ofthe furnace 10 wherein the furnace 10 may be tilted to pour off a slaglayer or to empty a charge of molten material contained inside thefurnace.

Attached to the tilt follower beam 12 is a furnace structural frame 18which includes a hearth frame portion 20, a plurality of side frameportions 22-22 and an upper beam portion 24. It should be understoodthat a plurality of furnace structural frame members 18-18 are arrangedparallel to one another, spaced a predetermined distance apart andjoined by perpendicularly oriented "I" beam members 26-26 to comprise afurnace structural shell.

The hearth frame portion 20 of the furnace structural frame 18 includesan arcuate surface 28. A hearth cover 30 covers the arcuate surface 28,extend, for the length of the furnace 10 and acts as a continuoussupport for a plurality of layers of refractory materials.

A hearth reservoir 32 is comprised of a plurality of bottom layers ofrefractory materials 34-34 supported by the hearth cover 30 and aplurality of hearth reservoir walls 38-38 which are supported by therefractory layers 34-34 and which extend upwards to a predeterminedheight. A steel liner 36 disposed between the bottom refractory layers34-34 acts as a slip plane for the bottom refractory layers.

A sidewall portion 40 is disposed between one of the hearth reservoirwalls 38-38 and a roof portion 42. Another sidewall portion 43 which isfixed is disposed between the other one of the hearth reservoir walls38-38 and the roof portion 42. It is the sidewall portion 40 which moreoften is in need of repair or replacement. This may be because ofpossible damage thereto by a charging machine (not shown).

The roof portion 42 includes a plurality of refractory units 44-44 suchas bricks, for example, attached to a roof support beam 46 along anarcuate surface 48 with a plurality of metal hangers 50-50. A metalhanger 50 is comprised of a metal bar with one end turned at 90° acrossa wider flat side 52 (see FIG. 6) of the bar and another end which ispierced with a brick engagement dowel 54. During assembly of therefractory portion of the roof 42, each refractory unit 44 is held inposition by the engagement of a metal hanger 50 and an engagement dowel54 with a receiving portion 55 of the refractory unit 44.

As can be seen in FIG. 1, a plurality of refractory key blocks 56-56 aredisposed between the roof portion 42 and the sidewall portion 40 andbetween the roof portion 42 and the fixed sidewall portion 43. The keyblocks 56-56 are set into position after the sidewall portions are setinto position.

Before the description of the furnace 10 of this invention is completed,it becomes instructive to view a prior art furnace. FIG. 2 illustratesthe construction of a prior art furnace designated generally by numeral60. As can be seen in the drawing, a tilt follower beam 61 is supportedby a plurality of rollers 62-62. A hydraulic cylinder 63 actuates atilting motion of the furnace 60 to cause a slag layer contained insidethe furnace 60 to be poured off or to empty a charge of molten materialcontained inside the furnace.

A structural frame 64 is mounted on and supported by the tilt followerbeam 61 and is comprised of a hearth frame portion 65 which has anarcuate portion 66, a plurality of side frame portions 67-67, aplurality of sidewall beams 82-82 attached to the side frame portions67-67 and a roof support portion 69 having an arcuate portion 70.

The furnace 60 also includes a roof portion 71 which is supported by theroof support portion 69 and which is comprised of a plurality ofrefractory bricks 72-72 attached to the arcuate portion 70 with hangers73-73. Each hanger 73 may be similar if not identical to a hanger 50shown in FIG. 6. A bottom portion 74 is comprised of a plurality oflayers 75-75 of refractory bricks 76-76 and is supported by a hearthcover 77 which is in engagement with the arcuate portion 66. A steelsheet 79 is disposed between the layers 75-75. A sidewall portion 80 iscomprised of a plurality of refractory bricks 81-81 attached to thesidewall beams 82-82 with a plurality of metal brackets 83-83. Thesidewall portion 80 is disposed between the roof portion 71 and thebottom portion 74. A plurality of refractory key blocks 84-84 aredisposed between the sidewall portion 80 and the roof portion 71.

Unlike the furnace 10 of this invention, the sidewall beams 82-82 of theprior art furnace are affixed rigidly to and are an integral part of thefurnace structural frame 64. As such, the sidewall beams 82-82 are notremovably mounted to the furnace structural frame 64. Refractory bricks81-81 are removable only from the interior of furnace 60 becauseaccessibility to the bricks is precluded by the structural frame 64.Further, removal of the bricks 81-81 requires a cooling down of thefurnace 60 from an operating temperature typically in the range of 2000°F. Such cooling of the furnace 60 commonly results in thermal stressdamage to other refractory portions thereof.

The problem of replacement or repair of worn or damaged sidewallportions of prior art furnaces has been overcome with the furnace ofthis invention. In the furnace 10, the sidewall portion 40 isconstructed in a manner which facilitates repair without the need ofcooling down the furnace to a temperature which enables the repairoperation to be conducted from within the furnace. The sidewall portion40 includes a plurality of modular sections 85-85 each including anexternal support stucture 86 and a refractory portion 87. In a preferredembodiment, the refractory portion 87 is comprised of a plurality ofrefractory bricks 88-88. Support of each modular section of the sidewallportion 40 is provided by a mechanical engagement 89. Each modularsection 85 is secured to the frame 18 by a connective arrangement 90.

Viewing now FIGS. 3 and 4, there is shown a detailed view of one of themodular sections 85-85 which includes a plurality of refractory brick88-88 attached to an arcuate portion 102 of an external supportstructure 86 by metal hangers 50-50 shown in FIG. 6. The externalsupport structure 86 includes two spaced apart members 108-108 which areoriented vertically and two lift bars, an upper lift bar 110 and a lowerlift bar 112. The lift bars span between the vertically oriented members108-108.

As is shown in FIG. 1, the external support structure 86 of each modularsection 85 is secured to the furnace structural frame 18 at two pointsof mechanical engagement. Viewing now FIG. 4, mechanical engagement 89of a lowermost portion of the modular section with the furnacestructural frame 18 is provided by a notch 150 provided at a lowermostportion of each vertical member 108 and is engaged with a support 152attached to the furnace structural frame.

Mechanical engagement 90 of an upper portion 114 of the external supportstructure 86 is adjacent to a portion of the roof support beam 46 whenthe modular section 85 is set into position on the furnace 10 and issecured with mechanical fasteners.

Referring now to FIG. 5, there is shown an alternate embodiment of amodular section. In the alternative embodiment, a modular section 155comprises a cast, monolithic refractory element 157 secured to arcuateportion 159 of an external support structure 86 with metal anchors161-161.

Viewing now FIG. 6, there is shown an external lift mechanism 300positioned adjacent to a modular section 85 which is in need ofreplacement in preparation for removal of the modular section. Theexternal lift mechanism 300 is engaged with fork lift forks 301-301inserted through fork lift tubes 322-322. A lift bar 304 of the externallift mechanism is moved into position relative to the modular section 85such that a support cradle 302 engages the upper lift bar 110 of themodular section. An articulating assembly 307 comprises a hydrauliccylinder 306 which is mounted pivotally about a pin 314 and an engagingblock 308. The articulating assembly 307 is manually positioned suchthat the engaging block 308 engages the lower lift bar 112 of themodular section 85, such procedure requiring simultaneous pivotal motionof the articulating assembly 307 and extension or retraction of thehydraulic cylinder 306. With the articulating assembly 307 in engagementwith the modular section 85 requiring replacement, the external liftmechanism 300 is controlled to remove the modular section from thesidewall 40.

With a replacement modular section 85 fully supported by the externallift mechanism 300, the modular section is caused to be positioned intoa void in the sidewall portion 40 of the furnace 10 created by the priorremoval of a modular section therefrom. A combination of movements ofthe fork lift forks 301-301 and extension or retraction of the hydrauliccylinder 306 may be necessary to cause engagement of the notch 150 withthe support 152 (see FIG. 4). Further movement of the fork lift forks301-301 may be necessary to provide the final connective engagement 90whereafter the external lift mechanism 300 may be removed fromengagement with the modular section 85.

It is to be understood that the above-described arrangements are simplyillustrative of the invention. Other arrangements may be devised bythose skilled in the art which will embody the principles of theinvention and fall within the spirit and scope thereof.

We claim:
 1. A furnace, comprising:a frame; and a refractory liningwhich is attached to and supported by said frame, said refractory liningcomprising:a bottom portion which forms a leakproof reservoir forholding molten material; a roof portion which is spaced above saidbottom portion; and a sidewall portion which is disposed between saidbottom portion and said roof portion and which comprises a plurality ofmodular sections which are capable of being removed individually withoutthe need to enter the furnace to permit replacement of individual onesof the modular wall sections.
 2. The furnace of claim 1, wherein eachsaid modular section of said sidewall portion includes a plurality ofrefractory elements which are adhered together to help maintain saidelements in the configuration of said modular section.
 3. The furnace ofclaim 1, wherein each said modular section of said sidewall portionincludes an external support structure which is supported by a portionof said frame adjacent to said bottom portion of said refractory lining.4. The furnace of claim 3, wherein each said modular section includes aplurality of refractory elements which are adhered together and whereinsaid external support structure to which is attached the plurality ofrefractory elements of a modular section is mechanically secured to aportion of said frame adjacent to said roof portion.
 5. The furnace ofclaim 1, wherein each said modular section of said sidewall portion ofsaid refractory lining comprises a single cast, monolithic refractoryelement.
 6. The furnace of claim 5, wherein said monolithic refractoryelement is attached to a portion of an external support structure withhangers.
 7. The furnace of claim 6, wherein each said external supportstructure to which is attached a cast monolithic element is inmechanical engagement with a portion of said frame adjacent to saidbottom portion.
 8. The furnace of claim 6, wherein each external supportstructure to which is attached a modular section which comprises a castmonolithic element is mechanically secured to another portion of saidframe adjacent to said roof portion.
 9. A method of repairing a furnace,said method comprising the steps of:providing a furnace which includes aframe, a bottom refractory portion for holding molten material, a roofrefractory portion which is positioned above the bottom portion and asidewall refractory portion which is disposed between the bottom portionand the roof portion and which comprises a plurality of modularrefractory sections which are capable of being removed individuallywithout the need to enter the furnace to permit replacement ofindividual modular wall sections; from a position external to thefurnace, applying forces to a modular section which is in need ofreplacement to remove the modular section which is in need ofreplacement from the sidewall portion; and installing a replacementmodular section in place of the removed modular section.
 10. The methodof claim 9, wherein said method is capable of being performed when thefurnace is at an elevated temperature.
 11. The method of claim 9,wherein said method is performed when the furnace is at roomtemperature.
 12. The method of claim 9, wherein the modular section isremoved by the steps of:disengaging securing means associated with anexternal support structure of the modular section to which refractoryportions are attached from the frame adjacent to the roof portion;applying a force to the external support structure to facilitate removalof the modular section which is in need of replacement fromjuxtaposition with adjacent modular sections; and removing the modularsection which is in need of replacement from the furnace.
 13. The methodof claim 9, wherein removing force is provided by an external mechanicaldevice which is attached temporarily to the external support structureof the modular refractory section which is in need of replacement.